The majority of portable information devices such as a cellular phone, a personal digital assistance (PDA), a global positioning system (GPS) and the like include a small-sized keypad. A usable range of such a small-sized keypad has been gradually increased to memos, twitter, various data processing using a portable information device and the like as well as general short message service (SMS) input. In an IP TV or the like, the small-sized keypad is also drawing attention for its necessity as a simple message input device.
Currently, a Korean alphabet (Hangul) input via a small-sized keypad is performed using schemes in which characters on character keys and/or elements on function keys are combined to newly produce characters that are not defined on the keypad. Among them, so-called the Chun-Jee-In (Korean) scheme and the Easy Hangul (Korean) scheme have been widely used. The Chun-Jee-In scheme requires that a user be familiar with positions of consonants and exhibits several problem as follows: In case that a final consonant of a previous letter and an initial consonant of a subsequent letter are the same character or in case that a previous character and a subsequent character are allocated to the same key, a continuous input thereof cannot be performed, and upon any deletion, the entire letter should be deleted. Meanwhile, in the Easy Hangul scheme, since there are large number of consonants which are not exhibited on the keypad, naive users cannot know intuitively for the use and a fingering distance is relatively long due to the frequent use of “*” and ‘#’ buttons.
On the other hand, in an English input using a small-sized keypad, characters are arranged according to a simple dictionary order regardless of frequencies of use, so there is inconvenience that a button should be pressed several times in order to input even a character having a high use frequency. Furthermore, regardless of a user's skill, a next character can be inputted only when a cursor is moved to a next character line after flickering three times. In this case, when timing is not matched, there may occur an error that a different character is inputted in the present character line.
The following Table 1 shows frequencies of use for alphabetic characters used in entries of Concise Oxford Dictionary (11th edition revised, 2004). As known from Table 1, statistically, the frequency of use of five characters, i.e., E(11.16%), A(8.50%), R(7.58%), I(7.54%) and O(7.16%) reaches approximately 41.95%. Accordingly, it can be seen that large deviations exist in the use frequencies of English alphabets.
TABLE 1E11.1607% 56.88M3.0129%15.36A8.4966%43.31H3.0034%15.31R7.5809%38.64G2.4705%12.59I7.5448%38.45B2.0720%10.56O7.1635%36.51F1.8121%9.24T6.9509%35.43Y1.7779%9.06N6.6544%33.92W1.2899%6.57S5.7351%29.23K1.1016%5.61L5.4893%27.98V1.0074%5.13C4.5388%23.13X0.2902%1.48U3.6308%18.51Z0.2722%1.39D3.3844%17.25J0.1965%1.00P3.1671%16.14Q0.1962%(1)
The Table 2 is derived by statistically analyzing characters of about 150 thousands acquired by extracting 2700 words from three different sources in the writing of Robert Edward Lewand, “Cryptographical Mathematics”. Table 2 shows frequencies of use for characters in a general English plain text. In this analysis, it can be seen that characters such as E, T, A, O, I, N, S, H, R, and the like are frequently used as compared to other alphabet characters. There is a minor difference in analysis results of Table 1 and Table 2, but some levels of similarity exist in overall distribution of the use frequencies between the two results.
TABLE 2CharacterFrequencyCharacterFrequencyA8.17%n6.75%B1.49%o7.51%C2.78%p1.93%D4.25%q0.10%E12.70% r5.99%F2.23%s6.33%G2.02%t9.06%H6.09%u2.76%I6.97%v0.98%J0.15%w2.36%K0.77%x0.15%L4.03%y1.97%M2.41%z0.07%
As such, despite the deviation in the use frequencies of characters, in a current input scheme using a small-sized keyboard, including a Roman alphabet input scheme such as English or the like and a Chinese Pinyin input scheme, the same button has to be pressed three times at the time of inputting alphabets I, O, and R having high use frequency.
Also in Japanese characters, there are characters which can be inputted by pressing the same button five times since five characters are disposed on one button.
As described above, the small-sized keypad has a problem that the number of pressing operations for inputting a character is increased when the character is disposed at the back on a button.
In addition, the existing small-sized keypad has only character buttons, so that short message service (SMS) input can be performed easily, but does not have various function keys, which causes difficulties in processing various data, including use of Internet or the like. Thus, a smart phone or the like uses a Qwerty keyboard including function keys, but an input is not easy due to its small size, which becomes an obstacle in miniaturization and slimness.
Therefore, there have been a demand for a small-sized keypad or a character and function key input device capable of compensating for defects in a scheme of inputting Korean, Roman character such as English, and Japanese.